Dispensing head mounted on a mobile hollow actuating shaft

ABSTRACT

A dispenser head comprising a connection sleeve ( 20 ), a dispenser orifice ( 31 ), a duct ( 123 ) connecting said connection sleeve ( 20 ) to the dispenser orifice, and a press surface ( 11 ), the head further comprising a shutter ( 4 ) that is housed, at least in part, in said duct ( 123 ), and that is resiliently biased by spring means ( 47 ) towards said dispenser orifice ( 31 ), said shutter ( 4 ) including a contact zone ( 41 ) that bears in resilient leaktight manner against the dispenser orifice ( 31 ) so as to seal it hermetically, said shutter being axially movable against the spring means in such a manner as to withdraw its contact zone from the dispenser orifice, thereby creating an outlet passage for the fluid, the shutter including at least one abutment zone ( 440 ) that is resiliently biased by the spring means against a fixed support zone ( 34 ).

FIELD OF THE INVENTION

The present invention relates to a dispenser head designed to be mountedon a movable hollow actuator rod which serves as a delivery channelmounted on the outlet of a fluid dispenser member such as a pump or avalve. A conventional design for a pump or a valve provides a hollowactuator rod through which the fluid under pressure is delivered to thedispenser head. Usually, the dispenser head includes a connection sleevedesigned to be engaged on the open free end of the movable actuator rod.Under such circumstances, the head also defines a dispenser orificewhich is connected to the connection sleeve via an internal duct. Inaddition, the dispenser head is provided with a press surface on whichit is possible to press by means of one or more fingers in order to movethe head axially, and consequently drive the hollow actuator rod intothe dispenser member.

The present invention relates more particularly to the type of dispenserhead incorporating a shutter, i.e. a device enabling the dispenserorifice to be closed. Thus, the fluid stored inside the head iscompletely isolated from the outside, and thus cannot be spoilt byoxidizing or by drying-out. By definition, the shutter closes thedispenser member where the fluid is dispensed out from the head.However, it is possible for the shutter to be situated a littleupstream, i.e. inside the dispenser head, with the device stillconstituting a shutter.

BACKGROUND OF THE INVENTION

In conventional manner, that type of shutter is situated, at least inpart, inside the duct connecting the dispenser member to the connectionsleeve. In addition, the shutter is often resiliently biased by springmeans towards the dispenser orifice. Under such circumstances, it shouldbe understood that the shutter is an internal shutter situated insidethe dispenser head, and that the dispenser orifice is opened byretracting the shutter further into the dispenser head.

Document FR-2 654 079 describes a dispenser head incorporating such ashutter. In that document, the shutter is housed inside the dispenserhead below the press surface on which it is possible to press in orderto actuate the dispenser member. At one of its ends, the shutterincludes a plunger pin designed to come selectively into leaktightcontact with the dispenser orifice. At its opposite end, the shutterdefines spring means in the form of an elastically deformable stripwhich bears against the body of the dispenser head. Furthermore, shutterdisplacement means are provided in the form of a cam secured to thebearing surface. Under such circumstances, the bearing surface iselastically deformable so that it is possible to press down the camthrough the shutter, which thus forms an actuator window. By loweringthe cam in this way, by pressing down on the press surface, the shutteris moved towards the inside of the dispenser head by deforming itsresilient strip. This movement withdraws the plunger pin from thedispenser orifice, and thus releases an outlet passage for the fluidunder pressure.

In the dispenser head in that French document, the shutter is moved torelease the dispenser orifice by means of a cam, as described above.However, other means for moving the shutter can be envisaged. Forexample, the shutter can form a piston slidably housed inside a chamber.Thus, when the fluid under pressure arrives in the chamber, the pistonis pushed back to slide against spring means, thereby withdrawing theplunger pin from the dispenser orifice. Consequently, it can be seenthat various means for moving the shutter are possible. In any event,the present invention relates more particularly to shutters having aplunger pin that is resiliently biased by spring means.

In dispenser heads having shutters that are resiliently biased, it isvery difficult to control the force with which the spring means pressthe plunger pin into the dispenser orifice. Naturally, the force isproportional to the intrinsic stiffness of the spring means, but it isalso proportional to their position inside the dispenser head.Furthermore, friction forces have an influence on the pressure force. Amajor drawback with that type of shutter resides in the fact that,sometimes, the plunger pin is pressed too far into the dispenser orificeso that it remains jammed therein. It is then no longer possible to usethe dispenser head, and consequently the dispenser member (the pump orthe valve). Furthermore, even when the plunger pin does not remainliterally jammed in the dispenser orifice, the shutter may remaintemporarily jammed, and that it bursts free suddenly when the presssurface of the dispenser head is pressed down hard. Thus, as a result,and contrary to the desired effect, the fluid is dispensed in a violentor explosive manner. Naturally, all of these drawbacks are associatedwith the lack of mastery or of control over the thrust force exerted bythe spring means on the dispenser orifice.

SUMMARY OF THE INVENTION

Consequently, an object of the present invention is to remedy, or atleast to mitigate, the above-mentioned drawbacks of the prior art bydefining a dispenser head in which the resiliently-biased shutter bearsin controlled and constant manner on the dispenser orifice so that it isactuated in effective and constant manner.

In order to achieve the objects, the present invention proposes adispenser head designed to be mounted on a movable hollow actuator anddelivery rod of a fluid dispenser member, said head comprising aconnection sleeve designed to be engaged on said movable rod, the headdefining a dispenser orifice, a duct connecting said connection sleeveto the dispenser orifice, and a press surface which can be pressed inorder to move the head axially by pushing the hollow rod into thedispenser member, the head further comprising a shutter that is housed,at least in part, in said duct, and that is resiliently biased by springmeans towards said dispenser orifice, said shutter including a contactzone that bears in resilient leaktight manner against the dispenserorifice so as to seal it hermetically, said shutter being axiallymovable against the spring means in such a manner as to withdraw itscontact zone from the dispenser orifice, thereby creating an outletpassage for the fluid when sufficient pressure is exerted on the presssurface, the dispenser head being characterized in that the shutterincludes at least one abutment zone that is resiliently biased by thespring means against a fixed support zone, the abutment zone thus takingup a portion of the thrust force generated by the spring means so thatthe contact zone bears with a constant limited force against thedispenser orifice. Thus, a constant and limited thrust force isguaranteed for the shutter at the dispenser orifice since the excessthrust force is taken up by the abutment zone. The abutment zoneadvantageously includes plane abutment surfaces that are situated insymmetrical manner about the travel axis of the shutter, the abutmentsurfaces coming to bear on associated plane support surfaces.

In a practical embodiment, the shutter comprises a plunger pin connectedto a shoulder, the plunger pin thus defining a free end forming thecontact zone designed to close the dispenser orifice selectively, theshoulder defining the support zone. The plunger pin advantageouslyextends into an outlet section of the duct that includes an inlet enddefining the support zone and an outlet end defining the dispenserorifice.

In another aspect of the invention, the outlet section is formed withguide splines that project inwards so as to hold the plunger pin on thetravel axis of the shutter. Not only is it impossible for the plungerpin to be jammed inside the head, but the plunger pin is also accuratelycentered on the dispenser orifice.

Still in a practical aspect, the dispenser head comprises a body, and adispenser endpiece connected in sealed manner on the body, the endpieceforming the duct and the dispenser orifice.

According to another characteristic of the invention, the dispenser headfurther comprises a displacement cam designed to come into engagementwith the shutter so as to move it when sufficient pressure is exerted onthe press surface, said cam being designed to come into engagement withan amplification cam so as to amplify the movement of the shutter.Advantageously, the connection sleeve is made integrally as a singlepiece with the displacement cam, the amplification cam being secured tothe press surface.

In another aspect of the invention, the spring means are made integrallyas a single piece with the shutter in the form of an elasticallydeformable loop. At least one of the dispenser orifice and the contactzone advantageously presents a frustoconical configuration. Contact ispreferably made cone on cone, with cones that are not necessarilyidentical so that there is no extended frustoconical contact, but merelyannular contact at the position where the two truncated cones touch. Inaddition, it is advantageous for the contact at the abutment zone to beof the plane on plane type, or at least on a plane that is perpendicularto the travel axis of the shutter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described more fully below with reference to theaccompanying drawings which show an embodiment of the invention by wayof non-limiting example.

In the figures:

FIG. 1 is a vertical section view through a dispenser head of theinvention;

FIG. 2 is a vertical section view through the FIG. 1 dispenser head atits dispenser orifice;

FIG. 3 is a horizontal section view from above of the FIG. 1 dispenserhead; and

FIG. 4 is a view similar to that of FIG. 1 while dispensing a fluid.

DETAILED DESCRIPTION OF THE INVENTION

The dispenser head shown in the figures comprises four componentelements, namely a body 1, a connection piece 2, a dispenser endpiece 3,and a shutter 4. In this embodiment, the four component elements aredistinct and separate from one another, but it is very easy to envisagevariant embodiments in which some of the component elements are madeintegrally as a single piece. For example, it is possible to envisagethat the dispenser endpiece and the body are made integrally as a singlepiece. It is also possible to envisage that the connection piece and thebody are made integrally as a single piece. In contrast, it is alsopossible to envisage that some component elements can be made up of twoor more pieces that are initially separate, and that are fitted orfastened together during assembly. All the component elements, namelythe parts 1 to 4, can be made of molded plastics material. However,other materials, and other manufacturing techniques, are not excluded.

The body 1 includes a skirt 10 which is generally cylindrical in shape.The body 1 is open at its bottom end, and closed at its top end by awall defining a press. surface 11 which can be pressed by means of oneor more fingers. Furthermore, the skirt 10 defines a lateral openingserving as a housing 12 for receiving the dispenser endpiece 3, asdescribed below. The housing 12 comprises a front bearing surface 121,and an inside wall 122 defining a snap-fastening rim 13. In addition,the press surface 11 is provided with a transverse web 14 which extendsdownwards from its bottom face. The transverse web 14 forms an inclinedsurface serving as an amplification cam 15, as described below. Theamplification cam 15 slopes away from the housing 12. Where it connectswith the skirt 10, the press surface 11 also forms an abutment housing110 whose function is described below. In addition, the skirt 10 forms asnap-fastening housing 101 designed to receive the connection piece 2.

The connection piece 2 includes a snap-fastening ring 21 that is snappedinto the housing 101 formed by the skirt 10 of the body 1. Theconnection piece 2 also includes a connection sleeve 20 which isdisposed inside the ring 21. The connection sleeve 20 is designed to beforce-fitted onto the top end of a hollow actuator rod defining aninternal fluid delivery channel. The actuator rod forms an integral partof a fluid dispenser member (not shown) such as a pump or a valve. Theend wall of the connection sleeve 20 is pierced by a passage 23 whichenables fluid to flow into the top portion of the body, just below thepress surface 11. In addition, the connection piece 2 forms adisplacement cam 24 presenting a cam surface 241 and an amplificationedge 242. The connection sleeve 20 and the displacement cam 24 occupy asubstantially central position inside the snap-fastening ring 21. Theassembly formed by the sleeve 20 and by the cam 24 is substantiallyrigid, and is connected to the ring 21 by an elastically deformableconnection 22. The elastically deformable connection 22 can be made byjunction tabs or even by a continuous deformable plate which extends allaround the sleeve 20 inside the ring 21. Thus, the sleeve 20 and the cam24 can be moved inside the ring 21, and consequently inside the body 1.The movement of the sleeve and of the cam can take place axially, i.e.vertically, and also laterally, i.e. radially. In other words, the cam24 can be moved vertically towards and away from the press surface 11,and also from front to back. Consequently, when sufficient pressure isapplied on the press surface 11, the actuator rod engaged in the sleeve20 moves the sleeve 20 and the cam 24 upwards towards the press surface11. The vertical movement is accurately axial until the amplificationedge 242 comes into sliding or rubbing contact against the amplificationcam 15 formed by the transverse web 14. From this moment on, thedisplacement cam 24 is moved laterally towards the righthand side inFIG. 1, while it is being moved vertically upwards. The amplificationcam 15 therefore increases the movement of the cam surface 241 of thedisplacement cam 24. The advantage of amplifying the movement of the cam24 in relation to the shutter 4 is described below.

The dispenser endpiece 3 is fastened in completely leaktight manner inthe housing 12 of the body 1 by snap-fastening. The dispenser endpiece 3is forced to bear against the front surface 121, and includes a sealedsnap-fastening sleeve 30 that is snapped into the cylinder 122. Thesealed snap-fastening sleeve 30 includes a snap-fastening profile 33which projects radially outwards so as to come into engagement behindthe snap-fastening edge 13 formed inside the housing 12. In this way,the dispenser endpiece 3 is held securely in the body 1, and both therim 13 and the front surface 121 are in leaktight contact with the body.The dispenser endpiece 3 defines an internal duct section 32 whichextends from an inside end, defined by the annular end 34 of thesnap-fastening sleeve 30, to an outside, other end which forms adispenser orifice 31. The internal duct section 32 also forms splines35, which can be seen more clearly in FIG. 2. The splines 35 serve asguide means for the shutter 3, as described below. In addition, the end34 of the sleeve 30 serves as a support zone or surface for the shutter4, as described below.

The body 1, the connection piece 2, and the dispenser endpiece 3 form aninternal chamber or duct 123 including an inlet 23 and an outlet 31. Thesection 32 forms a portion of the duct 123. The displacement cam 24 andthe amplification cam 15 are situated inside the duct 123.

In this case, the shutter 4 is situated completely inside the duct 123.The shutter forms a plunger pin 40 that is situated completely or inpart in the duct section 32, and a shoulder 44 is connected directly tothe plunger pin 40. The shutter also forms a drive portion 45 providedwith a cam window 450, and spring means 46, 47. The shutter canadvantageously be made as a single piece.

The purpose of the plunger pin 40 is to close the dispenser orifice 31formed by the endpiece 3 selectively. The plunger pin 40 includes a freeend forming a front wall 42, and a contact zone 41 designed to come intoleaktight contact against the dispenser orifice 31, so as to seal ithermetically. The plunger pin 40 presents a substantially constantcylindrical section having a diameter that is slightly less than thediameter inside the edges of the splines 35 so that the plunger pin 40is guided axially inside the duct section 32 with very limitedclearance. This thus ensures that the plunger pin 40 is accuratelycentered in the duct section 32, and thus on the dispenser orifice 31.At its end remote from the front wall 42, the plunger pin 40 isconnected to the shoulder 44 which defines two abutment surfaces 440designed to come into bearing contact against the support zone 34defined by the dispenser endpiece 3. Beyond the shoulder 44, thedisplacement cam 24 engaged in the cam window 450 passes through theshutter. The cam surface 241 is oriented so that upwards movement of thecam 24 causes the shutter 4 to be moved from the lefihand side to therighthand side in FIG. 1, i.e. causes the plunger pin 40 to be drivenfurther into the dispenser endpiece 3, thereby breaking the leaktightcontact with the dispenser orifice 31, and thus creating an outletpassage for the fluid under pressure. Furthermore, the inward movementof the plunger pin is increased by the amplification cam 15, whichdisplaces the cam 24 away from the dispenser orifice 31. Thus, withlimited vertical movement of the cam 24, significant movement of theplunger pin 40 is obtained inside the endpiece 3. Beyond the cam window450, the shutter 4 forms spring means, in this case in the form of atype of loop or toggle forming a base 46 bearing inside the housing 110,and two hinged legs 47 which provide the resilient characteristic. Inthe rest state shown in FIGS. 1 and 3, the resilient legs 47 areprestressed so that the plunger pin 40 bears, at its contact zone 41,against the dispenser orifice 31 while taking up the reaction force atits base 46. However, given that the shoulder 44 also comes intoabutment against the support 34 at an abutment zone remotely locatedfrom the contact zone, not all of the pressure force exerted by thespring means is exerted at the plunger pin 40. The support 34 thus takesup a portion of the pressure force exerted by the spring means, therebylimiting and stabilizing the thrust force at the dispenser orifice 31.Given that both the dispenser orifice 31 and the contact zone 41 presenta slightly frustoconical configuration in order to improve sealing,there is the risk of the plunger pin 40 becoming jammed in the dispenserorifice in the event of the pressure force not being taken up by thesupport 34. Both the abutment zone or surface 440 and the support zoneor surface 34 are substantially plane and perpendicular to thedisplacement direction of the shutter 4, thereby avoiding any riskofjamming or of gripping. The support 34 offers a clear bearingreference which makes it possible to modulate and stabilize the thrustforce of the plunger pin 40 against the dispenser orifice 31.

The dispenser head operates as follows. Starting from the rest positionshown in FIG. 1, it can be seen that the plunger pin 40 is engaged insealed manner in the dispenser orifice 31. By pressing on the presssurface 11, the actuator rod engaged in the connection sleeve 20 movesthe cam 24 upwards towards the press surface 11. In association with theamplification cam 15, the displacement cam 24 thus fulfils itsdisplacement function, and thus moves the plunger pin 40 towards theinside of the head, as can be seen in FIG. 4. The dispenser orifice 31is thus cleared and an outlet passage is thus created for the fluidunder pressure which is delivered by the actuator rod through the duct123 as far as the dispenser orifice 31. Releasing the pressure on thepress surface 11 enables the cam 24 and the sleeve 20 to return to theirinitial rest positions, as shown in FIG. 1. The plunger pin thus returnsto its rest position in leaktight contact with the dispenser orifice 31.The plunger pin is returned to said position by the spring means 47.

In the embodiment used to illustrate the present invention, the shutteris moved by means of a cam system. Other means of moving the shutter caneasily be envisaged, such as the pressure of the fluid inside the duct123, for example. The shutter can thus be formed with a piston slidingin sealed manner inside a slide cylinder. One of the advantageouscharacteristics of the invention resides in the fact that not all of thepressure force exerted by the spring means is exerted at the dispenserorifice.

1. A dispenser head designed to be mounted on a movable hollow actuatorand delivery rod of a fluid dispenser member, said head comprising aconnection sleeve (20) designed to be engaged on said movable rod, thehead defining a dispenser orifice (31), a duct (123) connecting saidconnection sleeve (20) to the dispenser orifice, and a press surface(11) which can be pressed in order to move the head axially by pushingthe hollow rod into the dispenser member, the head further comprising ashutter (4) that is housed, at least in part, in said duct (123), andthat is resiliently biased by spring means (47) towards said dispenserorifice (31), said shutter (4) including a contact zone (41) that bearsin resilient leaktight manner against the dispenser orifice (31) so asto seal the dispenser orifice hermetically, said shutter being axiallymovable against the spring means in such a manner as to withdraw thecontact zone from the dispenser orifice, thereby creating an outletpassage for the fluid when sufficient pressure is exerted on the presssurface, the shutter including at least one abutment zone (440) that isresiliently biased by the spring means against a fixed support zone(34), the abutraent zone thus taking up a portion of the thrust forcegenerated by the spring means so that the contact zone bears with aconstant limited force against the dispenser orifice, the dispenser headbeing characterized in that at least one of the dispenser orifice (31)and the contact zone (41) presents a frustoconical configuration; andwherein the shutter comprises an elongated plunger pin that extendswithin an elongated outlet section of the duct, the outlet sectionhaving an interior surface extending between the contact zone and theabutment zone, the interior surface opposing a facing exterior surfaceof the pin and spaced apart from the exterior surface of the pin.
 2. Adispenser head according to claim 1, in which the abutment zone includesplane abutment surfaces (440) that are situated in symmetrical mannerabout the travel axis of the shutter, the abutment surfaces (440) comingto bear on associated plane support surfaces (34).
 3. A dispenser headaccording to claim 1, in which the plunger pin (40) extends into anoutlet section (32) of the duct that includes an inlet end defining thesupport zone (34) and an outlet end defining the dispenser orifice (31).4. A dispenser head according to claim 3, in which the outlet section(32) is formed with guide splines (35) that project radially inwards soas to hold the plunger pin (40) on the travel axis of the shutter.
 5. Adispenser head according to claim 1, comprising a body (1), and adispenser endpiece (3) connected in sealed manner on the body, theendpiece (3) forming the duct (32) and the dispenser orifice (31).
 6. Adispenser head according to claim 1, further comprising a displacementcam (24) designed to come into engagement with the shutter so as to movethe shutter when sufficient pressure is exerted on the press surface,said cam being designed to come into engagement with an amplificationcam (15) so as to amplify the movement of the shutter.
 7. A dispenserhead according to claim 6, in which the connection sleeve (20) is madeintegrally as a single piece with the displacement cam (24), theamplification cam being secured to the press surface (11).
 8. Adispenser head according to claim 1, in which the spring means (47) aremade integrally as a single piece with the shutter (4) in the form of anelastically deformable loop (46, 47).
 9. A dispenser head according toclaim 1, wherein the plunger pin is connected to a shoulder, the plungerpin defining a free end forming the contact zone configured to close thedispenser orifice selectively, the shoulder defining the abutment zone.10. The dispenser head according to claim 9, wherein the plunger pinextends into the outlet section of the duct that comprises an inlet enddefinng the support zone and an outlet end defining the dispenserorifice.
 11. The dispenser head according to claim 10, wherein theoutlet section is formed with guide splines that project radiallyinwards so as to hold the plunger pin on the travel axis of the shutter.12. A dispenser head configured to be mounted on a movable hollowactuator and delivery rod of a fluid dispenser member, the headcomprising: a connection sleeve configured to engage the movable rod; adispenser orifice; a duct connecting the connection sleeve to thedispenser orifice; a press surface that when pressed moves the headaxially so as to push the hollow rod into the dispenser member; and ashutter housed, at least in part, in the duct and that is resilientlybiased by a spring towards the dispenser orifice, said shuttercomprising a contact zone that bears in resilient leaktight manneragainst the dispenser orifice so as to hermetically seal the orifice,the shutter axially movable against the spring so as to withdraw thecontact zone from the dispenser orifice, thereby creating an outletpassage for the fluid when sufficient pressure is exerted on the presssurface, the shutter comprising at least one abutment zone that isresiliently biased by the spring against a fixed support zone, theabutment zone taking up a portion of the thrust force generated by thespring so that the contact zone bears with a constant limited forceagainst the dispenser orifice; wherein at least one of the dispenserorifice and the contact zone is frustoconical and the abutment zone isremotely located from the contact zone; and wherein the shuttercomprises an elongated plunger pin that extends within an elongatedoutlet section of the duct, the outlet section having an interiorsurface extending between the contact zone and the abutment zone, theinterior surface opposing a facing exterior surface of the pin andspaced apart from the exterior surface of the pin.
 13. The dispenserhead according to claim 12, wherein the abutment zone comprises planeabutment surfaces situated in symmetrical manner about a travel axis ofthe shutter, the abutment surfaces coming to bear on associated planesupport surfaces.
 14. The dispenser head according to claim 12, furthercomprising a body and a dispenser endpiece connected in sealed manner onthe body, the endpiece forming the duct and the dispenser orifice. 15.The dispenser head according to claim 12, further comprising adisplacement cam configured to come into engagement with the shutter soas to move the shutter when sufficient pressure is exerted on the presssurface, said cam being designed to come into engagement with anamplification cam so as to amplify the movement of the shutter.
 16. Thedispenser head according to claim 15, wherein the connection sleeve ismade integrally as a single piece with the displacement cam, theamplification cam being secured to the press surface.
 17. The dispenserhead according to claim 12, wherein the spring is made integrally as asingle piece with the shutter in the form of an elastically deformableloop.
 18. The dispenser head according to claim 12, wherein the plungerpin has a diameter within the elongated outlet section that is less thana diameter of the opposing interior surface of the outlet section so asbe spaced apart therefrom and leave a gap.
 19. A dispenser head designedto be mounted on a movable hollow actuator and delivery rod of a fluiddispenser member, said head comprising a connection sleeve (20) designedto be engaged on said movable rod, the head defining a dispenser orifice(31), a duct (123) connecting said connection sleeve (20) to thedispenser orifice, and a press surface (11) which can be pressed inorder to move the head axially by pushing the hollow rod into thedispenser member, the head further comprising a shutter (4) that ishoused, at least in part, in said duct (123), and that is resilientlybiased by spring means (47) towards said dispenser orifice (31), saidshutter (4) including a contact zone (41) that bears in resilient leaktight manner against the dispenser orifice (31) so as to seal thedispenser orifice hermetically, said shutter being axially movableagainst the spring means in such a manner as to withdraw the contactzone from the dispenser orifice, thereby creating an outlet passage forthe fluid when sufficient pressure is exerted on the press surface, theshutter including at least one abutment zone (440) that is resilientlybiased by the spring means against a fixed support zone (34), theabutment zone thus taking up a portion of the thrust force generated bythe spring means so that the contact zone bears with a constant limitedforce against the dispenser orifice, the dispenser head beingcharacterized in that at least one of the dispenser orifice (31) and thecontact zone (41) presents a frustoconical configuration; and whereinthe dispenser head further comprises a displacement cam designed to comeinto engagement with the shutter so as to move the shutter whensufficient pressure is exerted on the press surface, said cam beingdesigned to come into engagement with an amplification cam so as toamplify the movement of the shutter.
 20. The dispenser head according toclaim 19, wherein the shutter comprises an elongated plunger pinconnected to a shoulder, the plunger pin thus defining a free endforming the contact zone designed to close the dispenser orificeselectively, the shoulder defining the abutment zone.